Pin valves are well-known in the art. This type of valve usually consists of a housing, a pin which travels back and forth within the housing to contact a seat at either end of the housing, a pin actuator to move the pin in a first direction, and a biasing spring to move the pin in a second direction. Fluid flows around the pin and into the housing from a preferably pressurized source when the pin is moved in the first direction, and the fluid flows from the housing, around the pin, and to a destination when the pin is moved in a second direction.
The above-described pin valve is commonly used in a fuel injector to aid the fuel injector's operation in a known manner by controlling the flow of engine oil to the fuel injector. While this prior art pin valve generally works well, there are some disadvantages in fluid control during a “cold start”, when the engine is completely cool. This happens quite often, for instance, when the engine is being started for the first time that day or after a few hours' rest.
It is important for the engine oil to be able to flow through the fuel injector at a predetermined rate, as the fuel injector's lubrication and performance characteristics are based on that predetermined rate. The predetermined rate is based on a certain viscosity value of the engine oil after the engine is “warned up”. Because the engine oil is very viscous and slow-flowing during a cold start, it does not flow through the pin valve as readily as when the engine is warmed up and the oil has a reduced viscosity from the engine's heat. The reduction of flow during a cold start can lead to lubrication and oil pressure problems within the fuel injector. Since solving this cold start problem by using less viscous oil would result in the warm oil being too thin to function as desired during most of the total operating time of the engine, it is desirable to instead route a larger volume (possibly via a higher flow rate) of the currently-used engine oil through the pin valve while the engine is cold than when the engine warms up. Currently the flow rate of the engine oil through the pin valve cannot be changed as the engine warms up.
Additionally, the dimensions of the pin valve and the fuel injector change minutely as the engine warms up, causing the metal to expand, and these dimension changes can alter the behavior of the valve and thus the oil, as well.
The present invention is directed to overcoming one or more of the problems as set forth above.